Seat belt retractor with torsion bar

Abstract

A seat belt retractor ( 10 ) includes a spool member ( 40 ) on which seat belt webbing ( 16 ) is wound. The spool member ( 40 ) is supported for rotation in a belt withdrawal direction ( 52 ) and an opposite belt retraction direction ( 54 ). The retractor ( 10 ) includes a plastically deformable torsion bar member ( 70 ) having a first portion ( 78 ) and a second portion ( 74 ). The second portion ( 78 ) of the torsion bar member ( 70 ) is rotatable relative to the first portion ( 74 ). The torsion bar member ( 70 ) twists upon rotation of the second portion ( 78 ) relative to the first portion ( 74 ). When the torsion bar member ( 70 ) twists, the spool member ( 40 ) rotates in the belt withdrawal direction ( 52 ) relative to the ratchet member ( 60 ), and the spool member cutter portion ( 92, 94 ) of the ratchet member cuts into the spool member ( 82, 84 ) to increase the resistance to rotation of the spool member relative to the ratchet member.

Having described the invention, I claim:  
     
       1. A seat belt webbing retractor comprising: 
       a spool member on which seat belt webbing is wound, said spool member being supported for rotation in a belt retraction direction and an opposite belt withdrawal direction;  
       a plastically deformable torsion bar member having a first portion and a second portion, said second portion of said torsion bar member being rotatable relative to said first portion, said torsion bar member twisting upon rotation of said second portion relative to said first portion;  
       an actuatable spool locking mechanism for when actuated blocking rotation of said spool member in the belt withdrawal direction, said spool locking mechanism including a ratchet member and a pawl movable into locking engagement with said ratchet member to block rotation of said ratchet;  
       one of said spool member and said torsion bar member and said ratchet member having a cutter portion;  
       said spool member being fixed for rotation with said first portion of said torsion bar member and said ratchet member being fixed for rotation with said second portion of said torsion bar member, said torsion bar member thereby resisting rotation of said spool member relative to said ratchet member;  
       said torsion bar member twisting and said spool member rotating in the belt withdrawal direction relative to said ratchet member and said cutter portion of said one of said members cutting into another one of said members to increase the resistance to rotation of said spool member relative to said ratchet member when said spool locking mechanism is actuated and upon the application of tensile force from the seat belt webbing to said spool member in an amount exceeding a predetermined amount;  
       said cutter portion moving into material of said another one of said members to separate some of the material of said another one of said members from said another one of said members;  
       said torsion bar member twisting and said cutter portion cutting at the same time.  
     
     
       2. A retractor as set forth in  claim 1  wherein said ratchet member has said cutter portion and said cutter portion cuts into said spool member. 
     
     
       3. A retractor as set forth in  claim 2  wherein said another one of said members has at least one lug that is cut into gradually by said cutter portion of said ratchet member upon rotation of said spool member in the belt withdrawal direction relative to said ratchet member during twisting of said torsion bar member. 
     
     
       4. A retractor as set forth in  claim 3  wherein said spool member has at least first and second lugs spaced apart from each other circumferentially about an axis of rotation of said spool member. 
     
     
       5. A retractor as set forth in  claim 2  wherein said cutter portion of said ratchet member comprises at least one cutting tooth that is engageable with said spool member to cut into said spool member upon rotation of said spool member in the belt withdrawal direction relative to said ratchet member. 
     
     
       6. A retractor as set forth in  claim 5  wherein said cutter portion of said ratchet member comprises at least first and second cutting teeth spaced apart from each other circumferentially about an axis of rotation of said spool member. 
     
     
       7. A retractor as set forth in  claim 1  wherein said spool member has said cutter portion and said cutter portion cuts into said torsion bar member. 
     
     
       8. A retractor as set forth in  claim 7  wherein said spool member is connected for rotation with said torsion bar member by a strippable connection that is adapted to strip when said spool locking mechanism is actuated and upon the application of tensile force from the seat belt webbing to said spool member in an amount exceeding the predetermined amount, said strippable connection resisting rotation of said spool about said axis by an amount that is greater than the resistance to spool rotation that is provided by said torsion bar member itself, whereby application of a force sufficient to cause twisting of said torsion bar member alone does not result in rotation of said spool relative to said ratchet in the belt withdrawal direction, and relative rotation of said spool does not occur unless there is stripping of said strippable connection between said spool and said torsion bar member. 
     
     
       9. A retractor as set forth in  claim 8  wherein said torsion bar member has a non-circular external configuration, said spool member having a portion having a similar internal configuration, said torsion bar member portion being received within said spool member portion to form said strippable connection. 
     
     
       10. A retractor as set forth in  claim 8  wherein said torsion bar member has a hexagonal external configuration received within a hexagonal internal configuration of said spool member portion to form said strippable connection. 
     
     
       11. A retractor as set forth in  claim 1  wherein said another one of said members has at least one separable portion that is cut into gradually by said cutter portion of said one member upon rotation of said spool member in the belt withdrawal direction relative to said ratchet member during twisting of said torsion bar member, and wherein said one separable portion is separated completely from said another one of said members after a predetermined amount of rotation of said spool member in the belt withdrawal direction relative to said ratchet member during twisting of said torsion bar member. 
     
     
       12. A retractor as set forth in  claim 1  wherein said ratchet has said cutter portion and member that is cut into comprises a projecting portion of said spool, said cutter portion and said projecting spool portion projecting radially, from opposite directions, into an annular space defined between said spool and said ratchet, said cutter portion and said projecting spool portion rotating together in said annular space. 
     
     
       13. A retractor as set forth in  claim 1  wherein said cutter portion cuts along a cylindrical path centered on an axis of rotation of said spool member. 
     
     
       14. A seat belt webbing retractor comprising: 
       a spool member on which seat belt webbing is wound, said spool member being supported for rotation in a belt retraction direction and an opposite belt withdrawal direction;  
       a plastically deformable torsion bar member having a first portion and a second portion, said second portion of said torsion bar member being rotatable relative to said first portion, said torsion bar member twisting upon rotation of said second portion relative to said first portion;  
       an actuatable spool locking mechanism for when actuated blocking rotation of said spool member in the belt withdrawal direction, said spool locking mechanism including a ratchet member and a pawl movable into locking engagement with said ratchet member to block rotation of said ratchet;  
       one of said spool member and said torsion bar member and said ratchet member having a cutter portion;  
       said spool member being fixed for rotation with said first portion of said torsion bar member and said ratchet member being fixed for rotation with said second portion of said torsion bar member, said torsion bar member thereby resisting rotation of said spool member relative to said ratchet member;  
       said torsion bar member twisting and said spool member rotating in the belt withdrawal direction relative to said ratchet member and said cutter portion of said one of said members cutting into another one of said members to increase the resistance to rotation of said spool member relative to said ratchet member when said spool locking mechanism is actuated and upon the application of tensile force from the seat belt webbing to said spool member in an amount exceeding a predetermined amount;  
       wherein said ratchet member has said cutter portion and said cutter portion cuts into said spool member;  
       wherein said spool member has at least one lug that is cut into by said cutter portion of said ratchet member upon rotation of said spool member in the belt withdrawal direction relative to said ratchet member;  
       wherein said spool member has at least first and second lugs spaced apart from each other circumferentially about an axis of rotation of said spool member; and  
       wherein the spacing of said first and second lugs about said axis is selected to initiate cutting of said second lug before cutting of said first lug is completed.  
     
     
       15. A seat belt webbing retractor comprising: 
       a spool member on which seat belt webbing is wound, said spool member being supported for rotation in a belt retraction direction and an opposite belt withdrawal direction;  
       a plastically deformable torsion bar member having a first portion and a second portion, said second portion of said torsion bar member being rotatable relative to said first portion, said torsion bar member twisting upon rotation of said second portion relative to said first portion;  
       an actuatable spool locking mechanism for when actuated blocking rotation of said spool member in the belt withdrawal direction, said spool locking mechanism including a ratchet member and a pawl movable into locking engagement with said ratchet member to block rotation of said ratchet;  
       one of said spool member and said torsion bar member and said ratchet member having a cutter portion;  
       said spool member being fixed for rotation with said first portion of said torsion bar member and said ratchet member being fixed for rotation with said second portion of said torsion bar member, said torsion bar member thereby resisting rotation of said spool member relative to said ratchet member;  
       said torsion bar member twisting and said spool member rotating in the belt withdrawal direction relative to said ratchet member and said cutter portion of said one of said members cutting into another one of said members to increase the resistance to rotation of said spool member relative to said ratchet member when said spool locking mechanism is actuated and upon the application of tensile force from the seat belt webbing to said spool member in an amount exceeding a predetermined amount;  
       wherein said ratchet member has said cutter portion and said cutter portion cuts into said spool member;  
       wherein said cutter portion of said ratchet member comprises at least one cutting tooth that is engageable with said spool member to cut into said spool member upon rotation of said spool member in the belt withdrawal direction relative to said ratchet member;  
       wherein said cutter portion of said ratchet member comprises at least first and second cutting teeth spaced apart from each other circumferentially about an axis of rotation of said spool member; and  
       wherein the spacing of said first and second cutting teeth about said axis is selected to initiate cutting of said spool member by said second cutting tooth before cutting of said spool by said first cutting tooth is completed.  
     
     
       16. A seat belt webbing retractor comprising: 
       a spool member on which seat belt webbing is wound, said spool member being supported for rotation in a belt retraction direction and an opposite belt withdrawal direction;  
       a plastically deformable torsion bar member having a first portion and a second portion, said second portion of said torsion bar member being rotatable relative to said first portion, said torsion bar member twisting upon rotation of said second portion relative to said first portion;  
       an actuatable spool locking mechanism for when actuated blocking rotation of said spool member in the belt withdrawal direction, said spool locking mechanism including a ratchet member and a pawl movable into locking engagement with said ratchet member to block rotation of said ratchet;  
       one of said spool member and said torsion bar member and said ratchet member having a cutter portion;  
       said spool member being fixed for rotation with said first portion of said torsion bar member and said ratchet member being fixed for rotation with said second portion of said torsion bar member, said torsion bar member thereby resisting rotation of said spool member relative to said ratchet member;  
       said torsion bar member twisting and said spool member rotating in the belt withdrawal direction relative to said ratchet member and said cutter portion of said one of said members cutting into another one of said members to increase the resistance to rotation of said spool member relative to said ratchet member when said spool locking mechanism is actuated and upon the application of tensile force from the seat belt webbing to said spool member in an amount exceeding a predetermined amount;  
       wherein said spool member has said cutter portion and said cutter portion cuts into said torsion bar member; and  
       wherein said torsion bar member is made from a softer material than said spool member and has a non-circular configuration that is stripped to a circular configuration by said cutter portion of said spool member when said spool locking mechanism is actuated and upon the application of tensile force from the seat belt webbing to said spool member in an amount exceeding the predetermined amount.